This invention relates to a process for the preparation of unsaturated ketones containing two glycidyloxy groups directly attached to carbon atoms of aromatic rings, and to such ketones prepared by the new process.
Certain ethylenically unsaturated ketones containing two glycidyloxy groups directly attached to carbon atoms of aromatic rings are known to be light-sensitive and have been used in the photochemical production of printing plates and printed circuits. Their preparation and use have been described in, for example, British Pat. No. 1,076,650 and U.S. Pat. No. 3,937,685.
These ketonic glycidyl ethers have been prepared by reaction of an unsaturated ketone having two phenolic hydroxyl groups with an excess of epichlorohydrin, usually under alkaline conditions. The unsaturated ketone having two phenolic hydroxyl groups has itself been prepared by reaction of two molar equivalents of a phenolic aldehyde with one molar equivalent of a ketone containing two active methylene groups, usually acetone. This process suffers from a serious disadvantage when carried out commercially. It has been found that, in order to obtain satisfactory yields, the reaction between the aldehyde and the ketone must be conducted in the presence of a large excess of an acid, gaseous hydrogen chloride usually being employed. This acid causes extensive corrosion when used on an industrial scale unless costly precautions precautions are taken. Further, extreme care is required in handling this acid.
It has now been found that the preparation of unsaturated ketones containing two O-glycidyl groups directly attached to aromatic rings may be effected entirely in the presence of an alkaline catalyst whilst still obtaining the good yields usually associated with acid catalysts. Further, the product has the high degree of purity necessary for its use in photopolymerisation applications. In this new method 2 molar equivalents of an o- or p-glycidyloxybenzaldehyde are condensed with one molar equivalent of a ketone containing two active methylene groups.